Steam generator



FIG. 1 is a rear upper perspective view of the steam generator showing my design;

FIG. 2 is a side view thereof; the opposite side being a mirror image;

FIG. 3 is a back view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof. 

I claim the ornamental design for a steam generator, as shown and decribed. 